1. Field of the Invention:
The invention is directed to apparatus and methods for heating spaces or curing crops and more specifically to heating and curing systems adapted to utilize engine heat as a heat source.
2. Description of the Prior Art:
Apparatus and methods for curing or drying of crops by circulation of pressurized air through a defined area or space have been documented in numerous prior patents. U.S. Pat. Nos. 3,105,713; 3,910,757; 3,972,674 and 3,999,303 are cited by way of example. U.S. Pat. Nos. 4,050,163; 4,003,139; 3,965,696 and 3,931,683 provides apparatus and methods for drying agricultural and other products and teach various means for maximizing the extraction of heat from heat sources.
Of particular interest to the present invention, reference is made to U.S. Pat. Nos. 2,343,346 and 2,479,526 which teach utilization of heat given off by a tractor engine for curing purposes in a barn.
The present applicant through Carolina Thermal Company of Reidsville, N.C., has sold a so-called "NR Power System" for barns equipped with a conventional furnace. This system utilized an LP gas engine as a heat source and to drive the fan but without the automatic control features of the present invention. Provision was made for an electric motor to drive the fan on engine failure. The NR system was withdrawn because of operational and mechanical problems and the need for an automatic control system which would allow automatic switching from one heat source mode to the other and vice versa. Also, the NR system revealed the special need for an automatic damper control.
A background article entitled "On Site Power Generation For C II Facilities" found in Specifying Engineer, November 1978, pages 96-101, discusses methods of recovery of heat energy from various sources.
There remains a need for a practical dual fan drive, heat and electrical power system for heating and drying crops. For example, the loss of air circulation in the event of an electrical power failure or failure of a primary heat source is critical in the curing of green leaf crops such as tobacco where a short period of two to four hours without forced airflow through the crop being cured may result in considerable economic loss. Thus, the provision of an improved heating apparatus and method designed to utilize recoverable engine heat, to protect against crop damage in the event of electrical power failures and to use an engine driven generator for loads normally electrically powered to realize energy savings are some of the objectives of the present invention.